Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Various applications require a nearly constant supply of reliable electrical power to operate effectively. For example, hospitals may require a constant and reliable supply of electricity to ensure medical equipment in operating rooms and the like function when needed. Further, food retailers such as supermarkets and grocery stores may require a constant and reliable supply of electricity to properly operate refrigeration systems associated with display cases and freezers to prevent food spoilage.
While utility companies generally provide electrical power consistently and reliably, such power is sometimes interrupted due to inclement weather, unforeseen accidents, or maintenance. Electrical power consumers seeking to mitigate or avoid even minor interruptions in their power supply often rely on generators and other backup systems to supply electrical power during periods when electrical service from a utility company is interrupted. Transfer switches enable these consumers to switch between a primary electrical source (e.g., from a utility company) and a secondary electrical source (e.g., a generator or other backup system) when one source becomes unreliable or requires maintenance.
Transfer switches may be manual transfer switches where, for example, an operator throws a switch to transfer power from one source to another. Additionally or alternatively, transfer switches may be automatic transfer switches where, for example, the switch automatically senses when a source has lost or gained power and responsively transfers power from one source to another. In one implementation, to transfer power between sources, the transfer switch may initiate a control sequence in which the transfer switch automatically starts a standby generator and then connects the standby generator to the load. The transfer switch may also automatically reconnect the utility power to the load if utility power is reestablished.
A bypass transfer switch may be used for applications where maintenance, inspection, and/or testing are performed while maintaining continuous power to the load. The bypass feature typically includes a secondary electro-mechanical switching device (bypass switch) that can route power to the load in a manner that circumvents a main transfer switch. This bypass feature allows, for example, (i) switch redundancy if a problem arises with the main transfer switch, (ii) exercising the main transfer switch without a load connection, and (iii) isolation for maintenance of the main transfer switch while ensuring the continuity of power to the load or loads. Any reference to transfer switch herein is meant to be non-limiting and broadly encompass any type of transfer switch.